Two identical positive charges are placed at $x =\, -a$ and $x = a$ . The correct variation of potential $V$ along the $x-$ axis is given by

An infinite nonconducting sheet of charge has a surface charge density of $10^{-7}\  C/m^2$. The separation between two equipotential surfaces near the sheet whose potential differ by $ 5\,V$  is

Two charge $ + \,q$ and $ - \,q$ are situated at a certain distance. At the point exactly midway between them

Three charges $q, \sqrt 2q, 2q$ are placed at the corners $A, B$ and $C$ respectively of the square $ABCD$ of side $'a'$ then potential at point $'D'$

A non-conducting ring of radius $0.5\,m$ carries a total charge of $1.11 \times {10^{ - 10}}\,C$ distributed non-uniformly on its circumference producing an electric field $\vec E$ everywhere in space. The value of the line integral $\int_{l = \infty }^{l = 0} {\, - \overrightarrow E .\overrightarrow {dl} } \,(l = 0$ being centre of the ring) in volt is

Two charged spheres of radii $10\, cm$ and $15\, cm$ are connected by a thin wire. No current will flow, if they have